Methods and devices that are used to group product units into product groups and to package them into boxes are known in many embodiments. The method-related procedure and a corresponding device to implement such a method in each case strongly depend on the type of product units.
Thus, for example, U.S. Pat. No. 5,732,536 shows a device by means of which adhesive tape can be packaged in boxes; the German published patent specification, examined only as to obvious defects but not as to patentability, DE2200390 shows a device for packaging, for example, household paper rolls; or EP350910 shows a device for packaging flower pots. The handling of different types of products requires correspondingly different methods and devices, and even in products that are apparently of the same type, depending on their size or design, different problems may occur which correspondingly also require differently matched methods and devices.
The present invention relates to a device and a method for packaging elongated, at least approximately hollow cylindrical, product units, preferably tubes, cartridges or cans, as known, for example, from EP1114784. This device is used per se, in particular, to form groups of elongated cylindrical product units that continuously arrive from a product line. The product groups formed are moved on a moving conveyor belt to a removal position from where they are pushed, layer by layer, into a box.
In a method known from CH682385, a compensator is interposed between a continuous supply and a discontinuous delivery, which compensator continuously receives the continuously supplied products and delivers them discontinuously. This takes place by way of a loop of a closed chain, which can be lengthened or shortened, which loop extends between an interposed receiving position and a delivery position.
From FR2391126 a device is known for grouping cylindrical product units that continuously arrive from a product line, and for conveying them in groups to a delivery position. In this design the conveyance and grouping devices comprise two transport slides that can move one behind the other and that are controlled in such a manner that one of them is loaded, while the other one moves to the delivery station where it is emptied. The emptied transport slide can then be moved back to the loading station, while the loaded station moves back to the delivery station. During the period of time in which no product units can be placed into the conveyance and grouping device, said product units are held back by a sluice flap.
A device according to EP0594917 operates in a similar manner. In this design, too, the conveyance and grouping device operates with two independently controlled transport slides, wherein, however, a conveyance device is arranged between the production line and the device for grouping the production units. Furthermore, the device comprises a shared transfer path in which the conveyance unit and the conveyor belt with the transport slides extend parallel to each other at some distance. In contrast to the arrangement with the previously described device, transfer to the conveying and grouping device takes place continuously and always in the same location.
In the device known from EP0774414 operation is by means of suction units that can be freely activated. Accordingly, it is extremely simple to remove product groups comprising different numbers of product units. Furthermore, the suction units can be accommodated in a gripper in which the grippers, matching the diameter of the product units, can be spaced apart from each other as required. On a delivery table that operates in a bellows-like manner, said grippers can be moved together to the diameter distance and can then be slid over into the corresponding shape. This device that operates with compressed air is, in particular, suited to production lines that operate at relatively low performance, wherein, however, changing the production line to different product units takes place relatively frequently. Since practically no conversion is required, in such cases the device pays off despite its expensive design. However, in the case of devices of the type mentioned in the introduction, where the production line is not frequently changed, such a device does not pay off because it operates too slowly.
WO2005019035 describes a device in which the product units are supplied on a conveyor belt comprising product receiving devices. When a predetermined number of product units are in the correct position the conveyor belt is stopped, and the product units are pushed, by means of a slider, onto a mandrel support. In this manner several rows of the product units are consecutively grouped to form a product group. This method is associated with a disadvantage in that each time during the transfer of the product units the conveyor belt needs to be stopped. Furthermore, a further row of product units can only be supplied after the slider has moved back. This has a significant negative effect on the overall processing speed of the grouping device and thus on the packaging costs.
In the machines present in today's market the tubes are either slid layer by layer into a corresponding box, or, as described in WO2005019035, are slid layer by layer for intermediate storage onto a plate-shaped mandrel support. The maximum throughput rates of conventional packaging devices range from 200 to 300 tubes per minute.